JP3417389B, published by the Japan Patent Office in 2003, discloses a device for controlling a power generation device installed in a hybrid electric vehicle in order to control charging of a battery.
This battery charging control technique uses road information such as a travel route, a travel distance and an altitude obtained from a car navigation system. A battery energy management upper limit value and a battery energy management lower limit value are set such that before a downhill slope, a remaining battery energy is as low as possible and before an uphill slope, the remaining battery energy is as high as possible.